Large-diameter earth boring bit

ABSTRACT

A bit for drilling large-diameter holes. Cutters are arranged in a staged configuration around a central shaft. The innermost cutters are the same large cutters used at other locations on the bit allowing complete interchangeability. The innermost cutters are turned inward. This reduces the uncut bottom next to the pilot hole and provides a stronger bit because the central shaft has not been weakened by milling or other operations.

United States Patent Inventor Milton L. Talbert China Springs, Tex.

Appl. No. 17,663

Filed Mar. 9, 1970 Patented Jan. 11, 1972 Assignee Dresser Industries,Inc. Dallas, Tex.

LARGE-DIAMETER EARTH BORING BIT 8 Claims, 5 Drawing Figs.

U.S. C1 175/334, 175/53, 175/344, 175/355 Int. Cl ..E2lc 23/00, E21d3/00, E2lb 9/24 Field of Search 175/62, 53, 334, 335, 342, 344, 350,353, 355-358 References Cited UNITED STATES PATENTS 3/1955 Westerman175/334 1,826,059 10/1931 Dunn et a1. 174/334 3,285,355 11/1966 Neilsonet al.. 175/334 1,322,696 11/1919 Hughes 175/353 2,064,273 12/1936 Scott174/342 X 2,122,808 7/1938 Catland.. 174/357 X 2,208,530 7/1940Thompson.. 174/335 3,437,380 4/1969 Lawrence 175/62 X Primary Examiner-David H. Brown Attarneys- Robert W. Mayer, Thomas P. Hubbard, .lr.,Daniel Rubin, Raymond T. Majesko, Roy L. Van Winkle, William E. Johnson,Jr. and Eddie E. Scott ABSTRACT: A bit for drilling large-diameterholes. Cutters are arranged in a staged configuration around a centralshaft. The innermost cutters are the same large cutters used at otherlocations on the bit allowing complete interchangeability. The innermostcutters are turned inward. This reduces the uncut bottom next to thepilot hole and provides a stronger bit because the central shaft has notbeen weakened by milling or other operations.

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INVENTOR MILTON L. TALBERT ATTORNEY PATENTEDJANI 1 29.72 3,633,691

SHEET3UF3 FIG. 4

MILTON L. TALBERT BACKGROUND OF THE INVENTION This invention relates tothe art of earth boring and more particularly to an improved bit fordrilling large-diameter holes. The bit of this invention is generallyused in a boring operation wherein a relatively small pilot hole isfirst drilled and the hole enlarged by a subsequent reaming operationutilizing the improved bit.

In bits of this character, it has been found desirable to employ anumber of small rolling or rotatable cutters rotatably mounted on a mainbit body. The cutters are located and spaced so that upon rotation ofthe bit every portion of the hole being drilled will be acted upon byone or more of the cutters to disintegrate the formation. This insuresthat almost the entire wear of drilling takes place on the cuttersrather than on the main bit body. The cutters should be readilyreplaceable thereby allowing the life of the bit to be extended byreplacing the cutters.

This type of bit is sometimes referred to as a raise bit" because of itsextensive use in boring raise holes between levels of an undergroundmine. The term raise" may have been applied to this type of operationbecause a pilot hole was drilled from one level of a mine down toanother level and the hole enlarged by a raising operation on the upwardpass. The bit of this invention may be used for boring raise holes andin other operations wherein a large-diameter hole is desired. This mayinclude boring at any angle to the horizontal either up or down and withor without a pilot hole.

Many strict requirements are imposed upon a bit to be used in boringlarge-diameter holes. The bit must be a balanced high-performanceapparatus that is rugged and will perform for a long period of time. Itis desirable to have a majority of the elements wear out at about thesame time without premature failure of any one element. The bit isrepeatedly subjected to high stress and the particular geometry of thebit imposes limitations upon the structural elements that are exposed tothe stress.

DESCRIPTION OF THE PRIOR ART The prior art is in general represented byU.S. Pat. No. 3,220,494 to R. E. Cannon et al., patented Nov. 30, 1965.The system shown by the Cannon et al. patent includes a rotary drillingapparatus for rotating and hydraulically raising a raise cutter headalong a pilot hole to form a raise hole between a lower level and anupper level of a mine. The raise cutter head enlarges the pilot byreaming with its plurality of staged cutters.

Large-diameter bits of the prior art have used different sized cutters.The inner cutters were generally smaller than the other cutters becausethey had to be located as close to the central shaft as possible and thesmaller the cutter the closer it could be to the central shaft. The useof different sized cutters creates problems, however, because they tendto wear out at different times and it is difiicult to provide a smallcutter that will withstand the high stresses encountered.

. SUMMARY OF THE INVENTION The bit of this invention has a plurality ofstages with each stage having a series of cutters surrounding a centralshaft. The consecutive stages progressively increase in diameter therebyallowing a pilot hole to be enlarged to the desired size. The stagedconfiguration provides a stabilizing effect which reduces wandering ofthe bit as drilling proceeds and helps maintain a smooth drillingoperation.

The individual cutters are removable which allows parts to be replacedwithout replacing the entire structure. The bit of this invention allowslarge cutters to be used on the innermost stage, thus providing completeinterchangeability of cutters on the bit which results in a bit that isstronger than those of the prior art. The use of large cutters on allstages of the bit also provides simplicity and economy to the drillingoperation.

The innermost cutters are turned inwardly. This provides room for thesaddle support next to the stern and consequently a stronger bit. Thereis little, if any, need to mill or relieve into the central shaft. inaddition, the unique inner cutters insure that there will be verylittle, if any, uncut bottom next to the pilot hole.

The cutters may be located close together which results in a bit that ismore compact than those of the prior art. The compactness providessimplicity, economy and a bit that is stronger than those of the priorart.

It is therefore an object of the present invention to provide a bit forboring large-diameter holes that is stronger and more efficient thanthose of the prior art.

It is a further object of the present invention to provide a bit fordrilling large-diameter holes that has interchangeable cutters.

It is a further object of the present invention to provide a bit fordrilling large-diameter holes that is more compact than those of theprior art.

It is a still further objective of the present invention to pro videgreater economy in boring large-diameter holes.

Itis a still further object of the present invention to provide a bitfor drilling large-diameter holes that eliminates the problemsassociated with having portions of uncut bottom next to the stem.

The above and other objectives and advantages will become apparent froma consideration of the following detailed description when taken inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a bit of the prior art.

FIG. 2 is an enlarged view of one of the small inner cutters of theprior art bit shown in FIG. 1.

FIG. 3 shows one embodiment of the present invention.

FIG. 4 is a top view of the bit shown in FIG. 3.

FIG. 5 is an enlarged view of one of the inner cutters of the bit of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a bit ofthe prior art is shown generally at 10. Two small inner cutters 1! and12 are positioned next to the central shaft 13 and function as the firstcutting stage. At least two cutters are used to insure a balanceddrilling bit and a smooth drilling operation. Cutters 1] and 12 are heldin position by saddles 14 and 15 which are mounted on central shaft 13.The saddles 14 and 15 allow the cutters to be easily removed and newcutters inserted. An example of a removable cutter and saddle system isshown in U.S. Pat. No. 3,203,492 to C. L. Lichte, patented Aug. 31,1965. A second cutting stage is located below the first stage andincludes two large cutters l6 and 17 mounted in saddles 18 and 19.

The central shaft 13 extends through a pilot hole having a diameterslightly larger than the diameter of shaft 13. The bit 10 is rotated bymeans of a system well known in the art. As bit 10 rotates the cuttersll, 12, 16 and 17 contact and disintegrate the formation as the bit ismoved along the pilot hole. The cutting surfaces of cutters l l, 12, 16and 17 must traverse the entire surface of the hole being bored and thesaddles and other portions of the bits must not contact the formationsbeing drilled. In order to accomplish this the inside cutting edges 20and 21 of cutters 11 and 12 must be as close to central shaft 13 aspossible and cutters 16 and 17 of the second cutting stage must bepositioned with their inside cutting edges below the outside cuttingedges of cutters 11 and 12. Consequently the inside cutters 11 and 12are limited in size and the central shaft must have a recess toaccommodate saddles 14 and 15.

Referring nowto FIG. 2, one of the inner cutters of the first stage isshown in greater detail. To insure that saddle 14 does not contact theformation being drilled, the axis 22 of cutter 11 is at an angle to axis23 of the central shaft 13. The angle 0 must be greater than 90 and isgenerally in the range of 120 to 130. The central shafi l3 must includea recess 24 to accommodate saddle l4 and cutter 11. The recess 24weakens the central shaft 13 and is therefore undesirable.

Referring now to FIG. 3, one embodiment of the present invention isshown generally at 25. One pair of inner cutters 26 and 27 arepositioned next to the central shaft 28. This pair of cutters 26 and 27is turned inward in a manner that will be explained more fully withregard to FIG. 5. A second pair of cutters 29 and 30 are included in thefirst stage. Cutters 29 and 30 are turned outward in the conventionalmanner but are set out from the central shaft 28 a sufficient distanceto accommodate the saddles for cutters 29 and 30 without requiring arecess in the central shaft 28. Cutters 31, 32, 33, and 34 make up thesecond stage ina manner similar to that described in connection withFIG. 1.

A top view of bit 25 is shown in FIG. 4. Inner cutters 26 and 27 arepositioned on opposite sides of central shaft 28 and turned inward. Theother pair of inner cutters 29 and 30 of the first stage are set outfrom central shaft 28 and turned outward. The second stage includingcutters 31, 32, 33, and 34 is located below the other cutters and spacedto provide a balanced bit. It can be appreciated that as the bit isrotated the cutters will contact all portions of the formation to insurea uniform drilling operation.

One of the inner cutters 26 is shown in greater detail in FIG. 5. Theaxis 35 of cutter 26 is at an angle 0 to the axis 36 of shaft 28. Theangle 0 is less than 90 and in this embodiment is an angle of 57". It isto be understood that d: may be an angle other than 57 and in general iswithin the range of from 45 to 90. The cutter 26 is the same size largecutter used at other locations on the bit 25. This incorporates all ofthe advantages of using large cutters including completeinterchangeability, greater strength, economy and a larger cutting area.The inner edge 37 of cutter 26 is located close to central shaft 28insuring that there will be very little, if any, uncut bottom next tothe central shaft. ln circumstances wherein a small amount of uncutbottom remains between point 37 and stem 36, the formation will breakaway much easier than when using bits of the prior art. Any uncut bottomwith bits of the prior art such as the bit shown in FIG. 1 will belarger than with a bit of this invention. In addition, the uncut bottomwill have greater support from the formation above because the cutter isat an obtuse angle. The saddle 38 supporting cutter 26 is positionednext to central shaft 28 without a large recess to accommodate it. Thisresults in a stem that is stronger than those of the prior art and ingeneral a bit that is stronger, more efiicient and compact than those ofthe prior art.

Referring again to FIG. 3, the operation of bit 25 will be described.The bit 25 is rotated and moved along a pilot hole according to a systemwell known in the art. The first pair of inner cutters 26 and 27 contactthe formationsnearest the central shaft and disintegrate them as the bitis moved along the pilot hole. It is to be understood that any number ofcutters may be used to carry out this operation. The bit should bebalanced so as to insure a smooth boring operation and in order tobalance the bit a plurality of cutters should be used, spaced at regularintervals around the central shaft. The second pair, of inner cutters 29and 30 contact the formations at a point spaced from the central axis.Cutters 29 and 30 may be slanted outward in the conventional mannerdescribed in connection with FIG. 1. The cutters 29 and 30 disintegratethe formations as the bit is moved along the pilot hole and protect thesaddles supporting cutters 26 and 27. In order to maintain a balancedbit it is to be understood that a plurality of cutters spaced at regularintervals may be utilized as previously discussed. The second stage ofcutters, including cutters 31, 32, 33 and 34, trail the first stage andenlarge the hole to the desired size. It is to be understood that morethan two stages may be provided if a still larger hole is desired andthat two stages are shown for illustration purposes.

The embodiments of the invention in which an exclusive propertg orprivilege is claimed are defined as follows:

1. A it for enlarging a pilot hole into a large-diameter hole dles, theaxis of rotation of said rolling cutters turned inward at an acute angleto the central longitudinal axis of said shaft; and

a second pair of rolling cutters, removably mounted in a correspondingsecond pair of saddles, the axis of rotation of said second pair ofrolling cutters tumed outward at an obtuse angle to the centrallongitudinal axis of said shaft.

- 2. The bit of claim 1 wherein the second of said drilling stagesincludes a plurality of rolling cutters removably mounted in acorresponding plurality of saddles, the axis of rotation of said rollingcutters turned outward at an obtuse an- 8 I I 3. The bit of claim 2wherein all of said rolling cutters are the same size.

4. The bit of claim 3 wherein said acute angle is within the range offrom 45 to 5. A bit for enlarging a small-diameter pilot hole into alarge-diameter hole comprising:

a central shaft having a central longitudinal axis, said central shafthaving an upper end adapted to fit within the pilot hole;

a main bit body attached to said central shaft, said main bit bodyhaving a diameter larger than the diameter of the pilot hole;

a plurality of drilling stages positioned on the main bit body,

said drilling stages progressively increasing in size;

the first of said drilling stages including a pair of rolling cutters,removably mounted in a corresponding pair of saddles, the axis ofrotation of said rolling cutters turned inward at an acute angle to thecentral axis of said shaft; and

the record of said drilling stages including a plurality of rollingcutters removably mounted in a corresponding plurality of saddles, theaxes of rotation of said plurality of rolling cutters turned outward atan obtuse angle.

6. The bit of claim 5 wherein all cutters are the same size.

7. The bit of claim 5 wherein said acute angle is within the range offrom 45 to 90.

8. The bit of claim 5 wherein said acute angle is approximately 5 7.

1. A bit for enlarging a pilot hole into a large-diameter holecomprising: a central shaft having a central longitudinal axis; a mainbit body attached to said central shaft, said main bit body including aplurality of drilling stages progressively increasing in size; the firstof said drilling stages including a pair of rolling cutters, removablymounted in a corresponding pair of saddles, the axis of rotation of saidrolling cutters turned inward at an acute angle to the centrallongitudinal axis of said shaft; and a second pair of rolling cutters,removably mounted in a corresponding second pair of saddles, the axis ofrotation of said second pair of rolling cutters turned outward at anobtuse angle to the central longitudinal axis of said shaft.
 2. The bitof claim 1 wherein the second of said drilling stages includes aplurality of rolling cutters removably mounted in a correspondingplurality of saddles, the axis of rotation of said rolling cuttersturned outward at an obtuse angle.
 3. The bit of claim 2 wherein all ofsaid rolling cutters are the same size.
 4. The bit of claim 3 whereinsaid acute angle is within the range of from 45* to 90*.
 5. A bit forenlarging a small-diameter pilot hole into a large-diameter holecomprising: a central shaft having a central longitudinal axis, saidcentral shaft having an upper end adapted to fit within the pilot hole;a main bit body attached to said central shaft, said main bit bodyhaving a diameter larger than the diameter of the pilot hole; aplurality of drilling stages positioned on the main bit body, saiddrilling stages progressively increasing in size; the first of saiddrilling stages including a pair of rolling cutters, removably mountedin a corresponding pair of saddles, the axis of rotation of said rollingcutters turned inward at an acute angle to the central axis of saidshaft; and the record of said drilling stages including a plurality ofrolling cutters removably mounted in a corresponding plurality ofsaddles, the axes of rotation of said plurality of rolling cuttersturned outward at an obtuse angle.
 6. The bit of claim 5 wherein allcutters are the same size.
 7. The bit of claim 5 wherein said acuteangle is Within the range of from 45* to 90*.
 8. The bit of claim 5wherein said acute angle is approximately 57*.